1. Field of the Invention
This invention relates to sampling network analyzers generally, and more particularly to sampling network analyzers which measure complex voltage, current, voltage or current ratio, phase angle, and power, including the contributions of harmonics of a fundamental Fourier component. Specifically, the present invention is directed to a such a sampling network analyzer in which there is included one or more controlled-gain amplifiers, where the voltage gain of such amplifiers may depart from their ideal, or exact, voltage gain. The invention is directed to an apparatus whereby the errors in mid-band voltage gain of such controlled-gain amplifiers are measured, typically in final test of the sampling network analyzer, and programmed into a programmable read-only memory (PROM). The PROM may also be programmed with measured values of the characteristic low-and-high-frequency cutoff values, to permit correction for the gain-vs-frequency characteristic of the amplifier or amplifier chain. The PROM becomes a part of the sampling network analyzer and, whenever a particular voltage gain of one of the controlled-gain amplifiers is invoked, at a particular frequency, the appropriate correction factor is made available to the instrument from the PROM.
2. Description of the Prior Art
The prior art includes several references directed to the concept of storing a correction signal in a memory for compensating various instrument response characteristics.
U.S. Pat. No. 4,149,120 decribes a stored program arrangement for correcting linearity of a test sensor.
U.S. Pat. No. 4,200,933 describes a microprocessor-controlled digital multimeter which includes self-calibration features, in addition to calibration constants.
U.S. Pat. No. 4,064,396, directed to a linearization system for a radiation gauge, includes a PROM which serves to store correction coefficients in the form of a set of digital signals.